A convergent synthesis of (+)-cryptophycin B, a potent antitumor macrolide from Nostoc sp cyanobacteria

[GRAPHICS] An efficient and highly stereoselective synthesis of cryptophycin B (2), a potent cytotoxic agent, is described. The ester-derived titanium-enolate-mediated syn-aldol reaction was employed to generate the stereocenters C(5) and C(6). The route is convergent and provides a convenient access to the synthesis of structural variants of cryptophycin B as well as members of its family.